This invention relates to exhaust systems for internal combustion engines and, more particularly, to a concentric dual exhaust system for a vehicle mounted internal combustion engine having a single manifold and concentric dual exhaust pipes.
It is known in the art relating to multi-cylinder internal combustion engines to provide in a single exhaust manifold, dual plenums for connection with diverse ones of the engine cylinders and having separate outlets for connection to separate exhaust pipes so as to provide separated dual exhaust passages over, at least, a portion of the length of the engine exhaust system. Such an arrangement is shown for example in U.S. Pat. No. 2,852,910 Wolfram, granted Sept. 23, 1958 to the assignee of the present invention. Such arrangements may be used, for example, to improve engine efficiency by reducing interference between exhaust pulses of adjacent cylinders or to provide reduced flow resistance in the exhaust system. More recently it has been recognized that such arrangements can be used to provide better defined pulsations in the exhaust system to aid the induction of secondary air to the engine exhaust passages through individual check valved inlet devices. Such a system may be used to eliminate the need for a separate air pump as provided in some commonly used secondary air injection (AIR) systems.